SKF rolling bearing clearance adjustment and preloading is an important part of the rolling bearing assembly work. Accurately grasp the process concept of clearance adjustment and preloading, and use this process method correctly in the assembly work is the guarantee of the quality of the bearing assembly work.
Overview of SKF rolling bearing clearance
The clearance of SKF rolling bearings refers to the maximum amount of movement of one ring in the radial or axial direction when the other ring is fixed. Therefore, the clearance is divided into radial clearance and axial clearance.
When the rolling bearing is assembled, its clearance cannot be too large or too small. If the clearance is too large, the number of rolling elements bearing the load at the same time will be reduced, and the load of a single rolling element will increase, thereby reducing the rotation accuracy of the bearing and reducing the service life; if the clearance is too small, the friction will increase and produce The increase in heat, aggravated wear, can also reduce the service life of the bearing. Therefore, many SKF bearings must strictly control and adjust the clearance during assembly.
Pre-tightening means that when the bearing is assembled, an axial force is given to the inner or outer ring of the bearing to eliminate the bearing clearance and cause the initial deformation of the contact between the rolling element and the inner and outer rings. Preloading can improve the stiffness and rotation accuracy of the bearing under working conditions. For SKF bearings that bear large loads and require high rotation accuracy, most of them work in a state of no clearance or even a small amount of interference. In this case, the bearing needs to be pre-tightened during assembly.
The adjustment and pre-tightening of the clearance are usually done by making the inner ring of the bearing an appropriate axial relative displacement to the outer ring.
It is not difficult to see from the above technological concepts that the bearing capacity and rotation accuracy of the bearing can be improved by adjusting the clearance of the rolling bearing, and the service life of the bearing can be improved. But at the same time, it will increase bearing friction and heat generation. Therefore, it is necessary to ensure good lubrication and heat dissipation while adjusting the clearance or preload. If it is improperly adjusted or poorly lubricated, it will in turn increase bearing wear and reduce life. Therefore, to correctly adjust and preload the rolling bearing clearance, pay attention to the following issues:
1. Assembly technical requirements are the fundamental basis for selecting assembly process methods
The adjustment of the rolling bearing clearance can effectively improve the rotation accuracy of the SKF bearing, increase the bearing capacity of the bearing, extend the service life of the bearing, and effectively reduce the vibration and noise. However, not all rolling bearings need to travel during assembly. Adjustment of the gap. Pre-tightening can certainly improve bearing rigidity and rotation accuracy, but at the same time it will increase friction, destroy the lubricating oil film and generate a lot of heat. Therefore, the pre-tightened bearing must be forced to lubricate and cool. This process method is limited to It is a relatively special process method that requires extremely high bearing rigidity and rotation accuracy. In actual production, it is only used in the assembly of machine tool spindles, and the bearing assembly of other transmission mechanisms is almost invisible. SKF 7311 BEP bearings online , pls click here :
2. To meet the requirements of clearance adjustment and preload under thermal equilibrium conditions
The actual ideal working clearance of SKF bearings is the clearance adjusted after the bearing temperature rises stably. Therefore, the adjustment of the SKF bearing clearance should be carried out in two stages: first, adjust the bearing clearance at room temperature in accordance with the relevant operating specifications and technical requirements, until the clearance is suitable and rotating by hand should feel flexible; then, the adjustment mechanism Properly loosen back (to prevent the bearing from locking up suddenly due to the temperature rise during the test run), and carry out the dry running test. The idle running time from low speed to high speed should not exceed 2 hours, and the idle running time at the highest speed should not be less than 30 minutes. Flexible operation, low noise, working temperature no more than 50, finally reset and lock the adjustment mechanism.
3. Maintain good lubrication
Good lubrication can not only reduce friction, but also cool the bearings and shaft parts. After the rolling bearing clearance is adjusted, the friction will increase, and the heat generated will increase the temperature of the entire transmission system.
If the heat can not be dissipated in time, the heat will change the size of the transmission parts, which will affect the change of the rolling bearing clearance, generate more heat, and form a vicious circle. Therefore, it is necessary to maintain good lubrication to reduce friction for rolling bearings that have undergone clearance adjustment, and more importantly, use continuously circulating lubricating oil to take away a lot of heat, control the temperature rise, and achieve the thermal balance of the transmission system.
4. Pay special attention
Before the dry running test, it is necessary to first check whether the lubrication system is supplied with oil normally, especially the preloaded bearing parts, and pay special attention to its sufficient lubricating oil supply and good working conditions.
In short, the correct assembly of SKF bearings according to the process, reasonable use, and careful implementation of the adjustment and pre-tightening process of the rolling bearing are effective means to improve the bearing rotation accuracy and load capacity, and reduce the vibration and noise of the transmission system. In addition to the rolling bearing assembly, the operation In addition to the general technical requirements, the impact of bearing temperature rise and lubrication on the adjustment work must also be considered, and careful inspection and secondary adjustment must be carried out after the dry running test, patient and meticulous.
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